Undetectable fault removal of sequential circuits based on unreachable states

Sequential redundancy removal using test generation and multiple unreachable states

“…We have proposed the procedure to find strongly unreachable states in [6,8] using next state functions of flip-flops.…”

“…We proposed the procedure to find removable faults in [6] using Theorem 1, which identifies removable faults by the following steps. Let state vector Su = ( F F I , FF2, ..., FFn) = (a,, a,, ..., a,) correspond to strongly unreachable states, where a, E { 0, 1, x(don't care)).…”

“…Our procedure in [6] checks only one strongly unreachable state vector at a time and does not require the state transition graph of the circuit. It have been reported that the procedure can find several removable faults in the benchmark circuits [6].…”

“…We define strongly unreachable states, which are states that have no incoming transitions from any states [6,8], to identify and remove undetectable faults. We have shown that the fault is removable if it affects the output functions and the next state functions only when the circuit starts from a strongly unreachable state [6].…”

“…We have shown that the fault is removable if it affects the output functions and the next state functions only when the circuit starts from a strongly unreachable state [6]. In our previous method in [6], undetectable faults are obtained using unreachable states based on [9].…”